DESCRIPTION: (Applicant's Abstract) Approximately half of injecting drug users (IDUs) and a quarter of crack smokers in New York City are infected with HIV. In "high-risk" neighborhoods with large concentrations of IDUs and crack smokers, this may pose a serious threat of sexual transmission of HIV to youth. Pilot data indicate that many such youth engage in unprotected sex with multiple partners and that they have very high rates of sexually transmitted diseases. We need to know which youth are most likely to have sex with IDUs and crack smokers, and thus to be at high risk for becoming infected with HIV; and which youth, in turn, are likely to have sex with the sex partners of IDUs and crack smokers. Youth who use heroin or cocaine (but who neither inject drugs nor smoke crack) may be very likely to have sex with IDUs and crack smokers, and, as a result, to be infected with HIV, hepatitis B, hepatitis C, and perhaps other STDs. (ln the pilot study, 79% of them were infected with herpes simplex virus type 2). Specific aims are to ascertain the prevalence among youth in a high-risk neighborhood of: (1) each drug-usage pattern; (2) high-risk sexual behaviors and high-risk sexual networks, and how these vary by drug-usage category; (3) infection with HIV, HBV, HCV and other STDs, and how these vary by drug-usage category. Also, (4) to determine social and personal risk factors for involvement in higher-risk drug usage, high-risk sexual behavior and high-risk sexual networks, and for HIV, its surrogate markers, and STDs. Since a pilot study indicated that many youth may have drug-use-resistant norms and attitudes, we aim to (5) determine the prevalence, determinants and behavioral effects of such norms and attitudes. (6) Available datasets on HIV prevalence and drug use among youth will be used to estimate the national generalizability of the findings on the prevalence of HIV and of drug-usage patterns. To answer these questions, a cross-sectional survey, including HIV and other testing, will be conducted of two samples of 18 to 24 year old youth in a high-risk Brooklyn neighborhood: (1) a probability sample of 700 household youth; (2) a targeted sample of 350 high-risk local youth who inject drugs or use crack, other cocaine, or heroin. Ethnographic research will study sexual relationships of these youth and the social and cultural forces that support and undermine youthful resiliency against high-risk sex and drug use. These findings can help target interventions where they are most needed and develop strategies to prevent high-risk drug use, high-risk sex, and infection with HIV.